Wireless network operators often desire to provide coverage over a well defined geographic area. Key to providing that coverage is ensuring good signal strength is available everywhere in that area. However, it would be a mistake to cover the area outside the desired geography as it is both wasteful of resources and potentially allows interference from outside the region to enter the network.
Historically, a network operator has had a selection of standard antennas for their base stations or wireless access point. For example, they might choose to use an omnidirectional antenna, a 90 degree sector, or a 120 degree sector. Each of these antennas is manufactured with dimensions to achieve the desired radiation pattern. Due to the nature of production line manufacturing, it is infeasible to manufacture unique antennas for each antenna site.
Furthermore, limited locations may be available to mount the antennas for a base station or wireless access point. For example, it may be desirable to use light poles to mount access points due to their height, but those light poles may not be in the best locations to provide wireless coverage. As such, it is often the case that the limited supply of antennas does not do an especially good job of covering an area of interest given the antenna locations that are available.
In contrast with traditional passive antennas, adaptive antennas are capable of creating a wide variety of patterns through software configuration. For instance, a phased array antenna's radiation pattern is determined by the “weights” that are programmed into the antenna (signal magnitudes and phases), along with physical parameters such as antenna element geometry and spacing. One example of a commercial phased array antenna is Fidelity Comtech's Phocus Array System.
The process of determining the set of weights (e.g., beamformer weights) that will produce a desired pattern is referred to as “pattern synthesis.” Historically, the pattern synthesis problem has been solved assuming there is a well defined radiation pattern that is desired of the antenna. The weights are then adjusted to attempt to mimic the defined radiation pattern. Occasionally, when there is an interfering signal that is jamming the desired signal, the weights are determined such that the ratio of the desired signal to undesired signal is minimized.